<template>
	<ul class="list">
		<li class="item" v-for="item of letters" 
		:key="item"
		:ref="item"
		@click="handleLetterClick"
		@touchstart="handleTouchStart"
		@touchmove="handleTouchMove"
		@touchend="handleTouchEnd"
		>{{item}}</li>
	</ul>
</template>
<script>
export default {
		name:'CityAlphbet',
		props:{
			cities:Object
		},
		computed:{
			letters(){
				const letters=[]
				for(let i in this.cities){
					letters.push(i)
				}
				return letters
			}
		},
		data(){
			return{
				touchStatus:false,
				startY:0,
				timer:null
			}
		},
		updated(){
			const startY=this.$refs['A'][0].offsetTop
		},
		methods:{
			handleLetterClick(e){
				this.$emit('change',e.target.innerText)
			},
			handleTouchStart(){
				this.touchStatus=true
			},
			handleTouchMove(e){
				if(this.touchStatus){
					if(this.timer){
						clearTimeout(this.timer)
					}
					this.timer=setTimeout(()=>{
						const touchY=e.touches[0].clientY-74
						const index=Math.floor((touchY-this.startY)/20)
						if(index>=0 && index<this.letters.length){
						this.$emit("change",this.letters[index])
						}
					},16)					
				}
			},
			handleTouchEnd(){
				this.touchStatus=false
			}
		}
}
</script>
<style lang="stylus" scoped>
  @import '~styles/varibles.styl'
  .list{
		display: flex
		flex-direction: column
		justify-content: center
		position absolute
		top: 1.58rem
		right 0
		bottom 0
		width .4rem
	}
	.item{
		line-height .4rem
		text-align center
		color $bgColor
	}
</style>